Long Term Verification Results and Reliability Improvement of M501G Gas Turbine

Abstract

Large combined cycle power plants utilizing advanced gas turbine technology are in demand worldwide due to attractive $/kw installation and operating cost advantages. A combined cycle plant has been operating since 1997 to determine the long-term reliability and hot parts durability of 1,500 degree C class M501G gas turbine technology that utilizes steam cooling of the combustor hardware. The verification is being conducted at MHI’s in-house combined cycle verification power plant known as T-Point. The verification is conducted while dispatching power to a local utility to augment the summer peak demand period. The gas turbine has accumulated over 12,000 actual operating hours and 650 start/stop cycles since it is primarily applied under Daily Start and Stop (DSS) duty. To date the availability has been 98.6 per cent, where Availability is defined as the actual power supply hours over the demanded power supply hours. The DSS duty imposes severe thermal-mechanical conditions that also facilitate in the accelerated assessment of the long-term reliability and parts durability. During the initial period of verification nearly 1,800 items were checked with special instrumentation, and about 1,000 items continue to be monitored in order to better quantify the physics. This has been supplemented by annual detailed overhaul inspections of the hardware to compare the accuracy of the predictions versus actual condition. Such inspections also included the rotor after approx. 10,000 operating hours to verify the integrity of all the parts in the rotor train. The knowledge and experience from the long-term verification has enabled several improvements because of valuable quantified data. (e.g enhancements, steam cooling effectiveness, etc.) Such verification data is critical for being able to introduce steam-cooled technology in new land based advanced gas technologies such as “G” and “H” class. Those are also important steps in commercial introductions of the M501G and M701G steam cooled combustor technologies. This paper describes results from the verification of the new technology with respect to operation, and design enhancements focused at reliability and hot parts life durability improvement.